net: do not call Windows TransmitFile for large files

TransmitFile does not allow for number of bytes that can be
transmitted to be larger than 2147483646. See

https://docs.microsoft.com/en-us/windows/win32/api/mswsock/nf-mswsock-transmitfile

for details. So adjust sendFile accordingly.

No test added, because this would require creating large file
(more than 2GB file).

Fixes #33193.

Change-Id: I82e0cb104d112264e4ea363bb20b6d02ac30b38e
Reviewed-on: https://go-review.googlesource.com/c/go/+/187037


Run-TryBot: Alex Brainman <alex.brainman@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com>